Thinking about a 0W-20 ? Need answers ?

[nrgetic99]

I was asked to comment on using an SAE 0W-20 oil in our applications versus the commonly used/required BMW High performance 5W-30.

I will start by saying I am not the person that formulated the BMW fluid but I did stay in a Holiday Inn Express last night. As such, I can address general technical points but no specifics.

SAE 5W-30 :


An SAE 5W-30 is a good oil for North America providing a good compromise of being thin enough to provide acceptable pumpability at low temps (the 5W ) yet remaining essentially thick enough to provide adequate protection at higher temperatures (the 30 part).

SAE 0W-20 :

A 0W-20 promises better pumpability at low temps (specifically slightly better performance 5 degrees C colder in testing) and a measurable benefit in fuel economy (measurable defined as 1% or greater) BUT is not as thick at higher temps so inherently, in warmer climes, or under extended high temp operations, in theory may not provide as good protection as the 'thicker' 30 grade.

Viscosity Index Improvers :

These fun little guys are essentially polymers dissolved in the oil that coil up at colder temps and maintain a good bulk oil thickness at cold temps and then straighten out at high temps to allow the oil to be the correct weight (not too thick) at high temps. Essentially, all multigrade lubricants have some form of Viscosity Index Improver in them with the exception of many fully synthetic oils as the properties of the full synthetic oils are such than you can avoid the use of VII's. This can be beneficial as over time, the VII can get chopped up and degraded by the bearings in the engine and the gears in the oil pump etc. This can lead to a loss of viscosity over time. Hence, one of a true synthetics advantages can be optimum cold and hot viscosity profiles without the need for a VII.

With me so far ??

Now here is where it gets fun...

SAE 5W-30 vs SAE 0W-20 :

In order to meet the viscometric requirements of a 0W-20, typically, we have to use thinner or lighter cuts of the base oils (typically 90% of your engine oil) which have two major negatives. 1. Volatility - essentially they are less resistant to being burned off at high temps and a little more susceptible to degradation (think of the excellent Castrol ad with the frying pan) and 2. Reduced film thickness.

Film thickness is what essentially , although tribologists will beat me for the oversimplification, what keeps the moving parts in bearing etc apart until the engine is at temperature and running above certain RPM's.

What an oil is trying to do is initially provide a physical barrier between the moving metal surfaces at low temps, low rpms until such time as we get full hydrodynamic lubrication when the fluid actually forms a 'fluid wedge' between the moving parts and holds them apart ...the ideal scenario as there is no contact.

So, in summary, a 0W-20 has real benefits in colder climes, it’s easier on the starter and electrical system and can give a fuel economy benefit BUT , if not formulated correctly, can give inadequate protection under higher temps.

How do we formulate 0W-20's ? :

Given the well known limitations of the thinner base oils required to make a 0W-20, most 0W-20's are synthetic. This is done for a couple of reasons. 1. Synthetic stocks are much more thermally stable and less prone of getting 'boiled off' at higher temps e.g. less volatile
2. Superior cold temperature properties without the need to resort to pour point depressants or additives designed to help conventional stocks perform better at low temps.
3. With the right synthetic base oils, we can eliminate or minimize use of Viscosity Index Improvers which may break down or shear down over time.

Esters :

However, pure synthetics have some disadvantages which are a result of how they are made ..namely, they are less likely to allow the other performance chemicals to dissolve and stay in solution and as you can imagine, an oil that separates out in use would be a disaster. So, we typically add some Ester which is another pure synthetic base stock which really helps the synthetic stocks solubilize or dissolve the other components effectively. Ester however is very expensive relatively so we do not use a great deal of it.

Coming back to my cold temp argument, Esters have a really good beneficial quality in so much as they are attracted to the surface of metals and provide an excellent film or protective layer in use and keep the metal surfaces apart until the speeds are great enough for this 'fluid wedge' to physically lift the surfaces apart.

So, now we have a base oil mix that provides exceptional cold temperature properties, is highly thermally stable AND when used with Ester, provides good if not better protection for the metal surfaces.

What about that -20 part , is the oil too thin ?

All lubricants have a major role to play in getting heat away from the critical parts of the engine and combustion process and getting to the cooling system to be transferred or just radiated away. One of a synthetics less known benefits is its ability to transfer heat away from the hot surfaces much more efficiently. So, what does this mean ? In essence, in use, a true full synthetic lubricant will not get as hot as it transfers the heat better so it will not get as thin in use as a non synthetic. In essence, a synthetic oil with a -20 grade could in fact be just as thick and provide just as much protection as conventional -30 grade.

So where does this leave us :

In essence, an SAE 0W-20 offers significant advantages in older temperatures of better cold flow, pumpabability and protection while the engine is cold. It can also provide benefits to the ancillary systemsin the vehicle and also can have a fuel economy benefit (this may be small). It does potentially have some debits in higher temperature operation BUT can be perform just as well if formulated correctly.
The major disadvantages are cost as a well formulated 0W-20 must use a true synthetic base oil in addition to some Ester or other component to aid solubility.

So what do I recommend ?? :

In a former life, I owned a 99 Toyota 4runner with a TRD supercharger and a variety of fueling and ECU mods that had a healthy 300 hp plus at the flywheel. In the winter, I ran an expensive genuine synthetic 0W-20 and found it had measurable benefits in starting in cold temps ( below zero) and fuel economy (close to 5%). I switched to a 5W-30 in the summer. I had the vehicle modified for a 60,000 miles and zero problems with engine.

Accordingly, if you would like to use a 0W-20 in the winter or if you find yourself in a colder region , provided you can establish it is a true synthetic (not a partial synthetic or a ‘marketing synthetic’ formulated with Group III base oils ), I do not foresee any issues. I have had good experience with the Mobil 1 0W-20 and 0W-30 products and also Amsoil Series 2000 0W-20. This however is my personal experience so I encourage you to do your own research. In the interests of full disclosure, I am not affiliated with Mobil or Amsoil nor am I in a position of supplying either company for these products…I purchased both of these products with my own hard earned cash.
David

[motordavid]

Intersting post, nrgetic...

Fwiw, I like and run the "euro" 0W-40 Mobil One, I cop at Walmart;
I like the 0W part for cold starts and the 40 for the high rpms we see
at cruise with our manual trans '01.

Another interesting post from a poster here, also a fellow lube eng.:
http://www.xoutpost.com/articles/x5/m...ion-101-a.html

His handle is "withidl" and he's put up some very comprehensive and informative posts, imo.
BR,mD

[bjo]

IMO its all good in theory. The main thing I have noticed about all oils is that they will shear down to a lower weight as they are used. So that 0w-20 can go to a lower weight depending on how the engine is stressed. I like to use the Mobil1 5w-40 oil made for turbo diesel trucks since it is a severe duty oil that does not shear so easily.

[chefwong]

What's the HTHS of this 0W20

[nrgetic99]

Originally Posted by chefwong

What's the HTHS of this 0W20

You ask what the HTHS is of 'this 0W-20'.

If you read what I wrote carefully, I do not recommend any particular 0W-20. I do however relate good experiences I have had with two partiuclar products.

I also urge people to do thier own research... in fact, I think you will find that was my exact words.

But, to be complete

The Amsoil Series 2000 0W-20 is no longer listed on their website but I had it measured at 3.0 cP (ASTM D4683).

They have now replaced that with thier signature series 0W-30 and do not offer a 0W-20 curently. The signature series 0W-30 is 3.2 cP.

Mobil 1 0W-20 is listed at 2.6 cP wheras the 0W-30 is listed as 2.99 cSt.

Do you have an absolute lower limit in mind and any data correlating HTHS to field performance, either good or bad ???

(The spec limit for a 30 weight is 2.9 cP min)

David

P.S. For those in the dark, HTHS measures the Viscosity at 150C and high shear condition such as in a bearing under load etc...it is really a good dynamic indicator of how a fluid holds up in real world conditions ....

[primetime]

So David. What are you running in your X in the winters? What were you running when you had the oil seperator issue? 5w -30?

[motordavid]

Originally Posted by primetime

So David. What are you running in your X in the winters? What were you running when you had the oil seperator issue? 5w -30?

PT, if your question is directed at me, I currently run the "euro" Mobil One 0W-40 for the past 18 months, (two changes)...

When we spent real winters, back on the mtn for the first 4 years of our X's "life", I ran 5W-30 syn in winter and, 5W-40 syn with occasional 15W-50 syn, in summer. I have never had an oil seperator issue. My cap looks clean and the beast still runs like a top with 64K miles and 6 1/2 yrs old.

Since we "winter" here in Naples, FL the past 3 winters, it's academic; still have last fall's change of the 0W-40 euro Mobil 1 in the crankcase.
BR, mD

[nrgetic99]

I am still running the BMW Genuine 5W-30 as it was recently changed just a few weeks before I bought the vehicle. I will look into a 0W-XX next winter. I was just asked in another thread what i thought of 0W-20's.

As for the degrading down argument, a well formulated true synthetic 0W-20 or 0W-30 does not need any Viscostiy Index Improver or Polymer so there is very little to shear down.

In fact in the Shear loss testing, it is normal to see neglible viscosity loss with two of the 0W-20's I have mentioned.

David

[primetime]

Originally Posted by nrgetic99

I am still running the BMW Genuine 5W-30 as it was recently changed just a few weeks before I bought the vehicle. I will look into a 0W-XX next winter. I was just asked in another thread what i thought of 0W-20's.

As for the degrading down argument, a well formulated true synthetic 0W-20 or 0W-30 does not need any Viscostiy Index Improver or Polymer so there is very little to shear down.

In fact in the Shear loss testing, it is normal to see neglible viscosity loss with two of the 0W-20's I have mentioned.

David

Thanks for the info...I was the one who asked about this in your other thread..I too will most likely switch to 0w - 20 next winter...

[primetime]

Originally Posted by motordavid

PT, if your question is directed at me, I currently run the "euro" Mobil One 0W-40 for the past 18 months, (two changes)...

When we spent real winters, back on the mtn for the first 4 years of our X's "life", I ran 5W-30 syn in winter and, 5W-40 syn with occasional 15W-50 syn, in summer. I have never had an oil seperator issue. My cap looks clean and the beast still runs like a top with 64K miles and 6 1/2 yrs old.

Since we "winter" here in Naples, FL the past 3 winters, it's academic; still have last fall's change of the 0W-40 euro Mobil 1 in the crankcase.
BR, mD

Sorry, I meant nrgetic..His name is David too..